End of maternity leave, sick leave and 13 weeks return to work

Hello,
I was a full time teacher before maternity leave and I was meant to return to work after maternity leave however I have been signed off sick and have handed in my sick note to my school. I am aware that holidays count towards the returning to work for 13 weeks in order not to have to pay back some of my maternity pay but does sick leave count towards this 13 weeks too?? As I will be starting at a new school in September.
Has anyone else been in this situation?